2. Field of the Invention
This invention relates to humidification systems that are used in heating, ventilating and air conditioning (HVAC) systems. Specifically, this invention relates to an improved apparatus for introducing steam into an airstream in such a system.
2. Description of the Prior Art
Inadequately humidified air can cause problems that range in severity from merely annoying to extremely expensive or even life threatening. Dry air can make people more susceptible to colds, sore throats and other respiratory problems. It can draw moisture out of materials such as carpet, wood, paper, leather, vinyls, plastics and foods. It can also contribute to generation of static electricity, which can damage electronically sensitive tapes and disks.
Most modern commercial and industrial buildings are equipped with steam humidifiers mounted within the heating and air conditioning systems. Steam from a steam boiler, district steam system or steam-generating humidifier is introduced into a ducted airstream and distributed throughout the building.
Humidification steam cannot be allowed to condense into water in a duct system. Damp areas in ducts become breeding grounds for algae and bacteria, many of which are disease-producing to humans, contaminating to industrial processes, and so forth. To prevent condensation in the duct, the steam must be totally absorbed by the air before the air carries the steam into contact with any internal devices such as dampers, fans, turning vanes etc., within the duct. The more thoroughly the steam is mixed with the air, the shorter the distance it will travel within the duct before becoming absorbed by the air.
Some duct configurations, due to structural limitations imposed by the building design, have very limited open space downstream of the humidifier for absorption of the steam. In order to overcome this problem, modern humidification systems typically utilize closely spaced steam dispersing tubes. Such dispersion tubes can present at least two operational difficulties when closely spaced.
First of all, present day steam dispersion tubes are usually constructed with an outer jacket which contains steam to keep the tube hot. This prevents humidification steam from condensing as it passes through the tube. In closely spaced multiple tube arrangements, such a configuration can present an impediment to air flow within the ducting system. Even more importantly, such a configuration can add unwanted heat to the airstream during periods of cooling. Insulating the exterior surfaces of the hot jacketing can reduce the heat gain, but further aggravates the air flow resistance problem. An automatic valve can be placed in the steam line, supplying steam to the tube jackets and cycling it off and on with the humidifier steam valve. When this has been done, in many cases, the flexing of the tubes caused by heating and cooling has led to eventual cracking of jacket welds.
It is clear there has existed a long and unfilled need in the prior art for a steam injection humidification system that is unaffected by condensation problems, and that is capable of introducing humidity into an airstream consistently and effectively.